Diaphragm valve for atomic layer deposition

ABSTRACT

A shut-off type diaphragm valve adapted for use in an atomic layer deposition system includes a flexible diaphragm operable to flex between an open position whereby a valve passage is at least partially open and a closed position whereby a substantial portion of a first side of the diaphragm is pressed against a valve seat to thereby block the valve passage and facilitate heat transfer between the valve seat and the diaphragm. In some embodiments, a heating body thermally contacts the valve body and extends proximal to a second side of the diaphragm opposite the first side thereof to form a thermally conductive pathway that facilitates maintaining an operating temperature at the diaphragm. A thermally resistive member may be interposed between the valve passage and an actuator, such as a solenoid, for attenuating heat transfer between the valve passage and the actuator.

RELATED APPLICATION

This is a continuation of and claims the benefit under 35 USC § 120 fromU.S. patent application Ser. No. 10/609,339, filed Jun. 26, 2003 (nowU.S. Pat. No. 7,021,330, issued Apr. 4, 2006), which is incorporatedherein by reference in its entirety.

BACKGROUND

This disclosure relates to a diaphragm valve that is particularly usefulin high-temperature thin film deposition systems and equipment.

Atomic Layer Deposition (“ALD”), also known as Atomic Layer Epitaxy(“ALE”), is a method of depositing thin films onto a substrate thatinvolves sequential and alternating self-saturating surface reactions.The ALD process is described in U.S. Pat. No. 4,058,430 of Suntola etal., which is incorporated herein by reference. ALD offers severalbenefits over other thin film deposition methods, such as Physical VaporDeposition (“PVD”) (e.g., evaporation or sputtering) and Chemical VaporDeposition (“CVD”), which are well known to those skilled in the art, asdescribed in Atomic Layer Epitaxy (T. Suntola and M. Simpson, eds.,Blackie and Son Ltd., Glasgow, 1990). ALD methods have been proposed foruse in depositing thin films on semiconductor wafer substrates, toachieve desired step coverage and physical properties needed fornext-generation integrated circuits.

Successful ALD growth requires the sequential introduction of two ormore precursor vapors into a reaction space around the substratesurface. Typically, ALD is performed at elevated temperatures andreduced pressures. For example, the reaction space may be heated tobetween 150° C. and 600° C., and operated at a pressure of between 0.1mbar and 50 mbar. Even at such high temperatures and low operatingpressures, pulses of precursor vapors are not delta functions, meaningthey have a substantial rise and decay time. Sequential pulses ofprecursor vapors will overlap if the second pulse is started before thefirst pulse is completely decayed, i.e., before excess first precursorvapor is substantially eliminated from the reaction space. Ifsubstantial amounts of the different precursor vapors are present in thereaction space at the same time, then non-ALD growth can occur, whichcan generate particles or non-uniform film thickness. To prevent thisproblem, the pulses of precursor vapor are separated by a purge intervalduring which the reaction space is purged of excess amounts of the firstprecursor vapor. During the purge interval, the reaction chamber ispurged by flushing the reaction chamber with an inert gas, applicationof a vacuum, pumping, suction, or some combination thereof.

The ALD reaction space is typically bounded by a reaction chamber, whichis fed by one or more precursor material delivery systems (also called“precursor sources”). The size of the reaction space is affected by thedimensions of the reaction chamber needed to accommodate the substrate.Some reaction chambers are large enough to fit multiple substrates forbatch processing. However, the increased volume of the reaction space ina batch processing system may require increased precursor pulsedurations and purge intervals.

To prevent overlap of the precursor pulses and to form thin films ofrelatively uniform thickness, an ALD process may require purge intervalsthat are ten times longer than the duration of precursor vapor pulses.For example, a thin film deposition process may include thousands ofprecursor vapor pulses of 50 ms duration alternating with purgeintervals of 500 ms duration. Long purge intervals increase processingtime, which can substantially reduce the overall efficiency of an ALDreactor. The present inventors have recognized that reducing the riseand decay times also reduces the overall time required for precursorpulse and purge without causing non-ALD growth, thereby improving thethroughput of the ALD reactor.

A precursor material delivery system may typically include one or morediaphragm valves positioned in a flow path of the system, for preparingand dispensing one or more precursor vapors. The precursor vapors arepulsed into the reaction chamber by opening and closing the appropriatediaphragm valves in the precursor delivery system. Diaphragm valves canalso be used for controlling the flow of inert gases and other materialsinto and out of the ALD reactor. Known diaphragm valves commonly have anactuator for opening and closing a flexible diaphragm against a valveseat. When the diaphragm is in the open position, the precursor vapor isallowed to pass through a valve passage and enter the reaction chamber.When closed, the diaphragm blocks the valve passage and prevents theprecursor vapor from entering the reaction chamber. Because ALDprocessing can require many thousands of cycles of precursor pulse andpurge for forming a film on a single workpiece, valves used in an ALDsystem should have very high durability and be able to perform millionsof cycles without failure.

Hydraulic and pneumatic actuators typically include dynamic seals thatcan fail under the high temperatures and large number of cycles requiredfor delivery of precursor gases and purge gases in an ALD system.

Solenoid type actuators are desirable because they typically have afaster response time than pneumatic and hydraulic actuators, and arecapable of a large number of open-close cycles. However, solenoidactuators generate heat when electric current is applied and, likehydraulic and pneumatic valves, solenoid actuated valves can fail whenexposed to the high temperatures required for maintaining some precursormaterials in vapor form. Heat can degrade the insulation around thesolenoid windings, resulting in electrical shorting between windings andfailure of the solenoid coil. It can also melt a plastic bobbin aroundwhich the solenoid coil is wound. The present inventors have recognizedthat active cooling of the actuator to avoid heat-related failure tendsto also draw heat from the diaphragm, valve seat, and walls of the valvepassage, which can cause the precursor material to condense or solidifyin the valve passage. Condensation and buildup of precursor material onthe diaphragm and valve seat can cause the valve to leak or clog,leading to undesirable non-ALD growth and particles in the reactionchamber.

For successful ALD processing, precursor gases are typically deliveredto the reaction chamber at temperatures in excess of 100° C. and oftenbetween 200° C. and 300° C., particularly the varieties of precursormaterials used for forming thin films on semiconductor substrates. Witha conventional diaphragm valve, a significant amount of heat isconducted from the flow path through the valve, where it dissipates tothe surrounding environment. Heat dissipation through the valve canresult in cooling of the flow path and the associated condensationproblems discussed above. To avoid condensation, the flow path may beheated, as described, for instance, in U.S. Provisional PatentApplication No. 60/410,067 filed Sep. 11, 2002, titled “PrecursorMaterial Delivery System for Atomic Layer Deposition,” which is owned bythe assignee of the present invention and incorporated herein byreference. However, heating the flow path may tend to contribute tooverheating of the actuators in conventional diaphragm valves. Thepresent inventors have recognized a need for an improved diaphragm valvein which the valve passage, diaphragm, and valve seat can be kept hotenough to prevent the precursor vapor from condensing (typically in therange of 130° C. to 260° C. or hotter), without overheating the valveactuator.

U.S. Pat. No. 5,326,078 of Kimura, U.S. Pat. No. 6,116,267 of Suzuki etal., and U.S. Pat. No. 6,508,453 of Mamyo describe known diaphragmvalves for controlling the flow of high temperature gases forsemiconductor manufacturing.

The present inventors have recognized that a need remains for a valve inwhich the diaphragm is kept at a temperature sufficient to preventcondensation of ALD precursor materials while not exceeding thetemperature limits of the actuator. The inventors have also recognized aneed for a durable valve that transitions from an open position to aclosed position more quickly than prior art valves.

SUMMARY

A shut-off type diaphragm valve includes a valve body defining a valvepassage having an inlet and an outlet and a valve seat adjacent thevalve passage. A flexible diaphragm is positioned adjacent the valvepassage opposite the valve seat with a first side of the diaphragmfacing toward the valve seat. The diaphragm is operable in response toan applied actuation force to flex between an open position whereby thevalve passage is at least partially open and a closed position whereby asubstantial portion of the first side of the diaphragm is pressedagainst the valve seat to thereby block the valve passage and facilitateheat transfer between the valve seat and the diaphragm. The actuationforce may be applied by a solenoid or hydraulic actuator, for example.

In some embodiments, a heating body thermally contacts the valve bodyand extends proximal to a second side of the diaphragm opposite thefirst side thereof to form a thermally conductive pathway thatfacilitates maintaining an operating temperature at the diaphragm. Athermally resistive member may be interposed between the valve passageand the actuator for attenuating heat transfer between the valve passageand the actuator. In one embodiment, a heater is thermally associatedwith the valve body and generates heat that is conducted through thevalve body and the heating body to prevent a medium in the valve passagefrom condensing or freezing in the valve passage.

Additional aspects and advantages of the invention will be apparent fromthe following detailed description of preferred embodiments, whichproceeds with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric section view of a precursor delivery systemincluding several diaphragm valves;

FIG. 2 is a cross section elevation view of one of the diaphragm valvesof FIG. 1, with a diaphragm of the diaphragm valve shown in a closedposition;

FIG. 3 is a cross section view of the diaphragm valve of FIG. 2, takenalong line 3—3 of FIG. 2;

FIG. 4 is an enlarged cross section view detailing the region of a valvepassage, valve seat, and diaphragm of the diaphragm valve of FIG. 2,with the diaphragm shown transitioned to an open position; and

FIG. 5 is an enlarged cross section view detailing the seating region ofa diaphragm valve including an alternative valve seat having a seatingridge suitable for use with a plastic diaphragm.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 is an isometric section view of a precursor material deliverysystem 100 of an ALD reactor 102, which comprises an exemplaryenvironment of use for valves 104 a–104 e, in accordance with a firstpreferred embodiment. With reference to FIG. 1, a supply of precursormaterial is stored in a precursor container 106, where it is heated andvaporized before flowing through a flow path 110 of the precursormaterial delivery system 100 (generally from left to right in FIG. 1)and into a reaction chamber 112. ALD reactor 102 will typically have twoor more precursor material delivery systems 100 connected to reactionchamber 112. Precursor material delivery system 100 includes electricheaters 116 and 118 for heating precursor materials in the flow path110. Valves 104 a–104 e are used to control the flow of precursormaterial and regulate pressure of the precursor vapor at differentstages in precursor material delivery system 100.

Precursor material delivery system 100 preferably includes removablemodules 120 having bodies 122 machined from solid blocks of thermallyconductive material, such as aluminum, titanium, or stainless steel.Modules 120 have various different functions, such as storage,vaporization, valving, filtering, and pulsing of precursor materials,and purging with inert gases. Modules 120 preferably all have a heavyconstruction that promotes diffusive conduction of heat from heaters 116and 118 to promote a smooth temperature gradient along the length ofprecursor material delivery system 100, increasing in temperature towardreaction chamber 112. The downstream heater 118 may operate at atemperature slightly higher than the upstream heater 116 to facilitatethe temperature gradient. In an alternative embodiment (not shown), agreater number of heating zones may be employed. A positive temperaturegradient is important for preventing undesirable condensation orfreezing of precursor gases in flow path 110 at any point downstreamfrom precursor container 106. The magnitude of the temperature gradientis not typically important, so long as the temperature and pressureconditions within flow path 110 are sufficient to prevent condensationor freezing of precursor vapors. To maintain vaporization, heaters 116and 118 may typically be operated at temperatures in the range ofapproximately 50° C. and 300° C.

A volume module 124 is provided downstream from the precursor container106 for preparing a dose of gas-phase precursor material. A particlefilter module 128 prevents particles from being transported fromprecursor container 106 into volume module 124. Valve 104 d is adiaphragm valve used to control the timing and duration of pulses ofprecursor vapor introduced into the reaction chamber 112 by precursormaterial delivery system 100. A diffusion barrier module 140 includesvalve 104 e for controlling the direction of an inert gas flow in abarrier section 144 of flow path 110 located between diaphragm valve 104d and reaction chamber 112.

FIG. 2 is a cross-section elevation view of a diaphragm valve 200 inaccordance with a preferred embodiment, which is exemplary of valves 104a–104 e (FIG. 1). With reference to FIG. 2, diaphragm valve 200 includesa valve body 210 that defines a valve passage 214 through which a mediumcan flow when diaphragm valve 200 is open. Valve passage 214 includes aninlet 216 and an outlet 218, which are selectively interruptible by aflexible diaphragm 220, which blocks valve passage 214 when flexed to aclosed position, as shown in FIG. 2. Valve body 210 is preferablyintegrally formed with the body 122 of one of the modules 120 ofprecursor material delivery system 100 (FIG. 1). Forming valve passage214 in module body 122 facilitates connection of inlet 216 and outlet218 to adjoining portions of flow path 110 in adjoining modules 120 ofprecursor material delivery system 100. Alternatively, valve body 210may comprise a separate structure, which, when used in an ALD precursormaterial delivery system 100, may be coupled to the module body 122.Valve body 210 is preferably formed from a solid billet of materialhaving good thermal conductivity. However, valve body 210 may,alternatively, be formed of multiple parts or by means other thanmachining from a solid billet, such as by molding or casting, forexample. Suitable valve body materials for use in ALD system 102 includealuminum, titanium, and stainless steel. Other materials such as copper,brass, other metals, and molded materials such as high temperatureplastics and molded metals may also be suitable for use in valve body210 depending on the environment in which diaphragm valve 200 is to beused.

In the preferred embodiment, inlet 216 and outlet 218 extend in agenerally axial direction relative to diaphragm valve 200. However, inalternative embodiments (not shown), valve passage 214 may include astraight-through passage extending transversely to diaphragm valve 200.Still further alternatives may include a weir formed in the valve bodybetween the inlet and outlet. Many other means and structures may beused for defining valve passage 214 to handle the flow of a medium suchas a fluid (liquid and/or gas) or slurry.

Inlet 216 and outlet 218 extend into a cylindrical blind bore 226bordered by a rim 228 against which diaphragm 220 is secured. Bore 226is deep enough to accommodate a valve seat 230 against which diaphragm220 is pressed when transitioned to the closed position. Bore 226 isalso sized to allow the medium to flow through valve passage 214 betweeninlet 216 and outlet 218 when diaphragm 220 is transitioned to the openposition (FIG. 4). Thus, bore 226 forms side and bottom boundaries of acentral chamber 232 (FIG. 4) of valve passage 214. In a preferredembodiment, diaphragm 220 is a flexible disc-shaped member having acentral section that is pressed against or pulled away from valve seat230 selectively in response to an applied actuation force. Diaphragm 220includes a first side 234 positioned proximal to valve passage 214 andforming an upper boundary of central chamber 232. A second side 236 ofdiaphragm 220 opposite first side 234 is engaged by a means for applyingactuation force, such as an actuator 240.

Diaphragm valve 200 is shown oriented with actuator 240 extendingvertically from diaphragm 220 and valve passage 214. However, diaphragmvalve 200 could also be oriented with actuator 240 extending to the sideof, below, or at an incline relative to diaphragm 220 and valve passage214. Furthermore, diaphragm 220, valve passage 214, and other parts ofdiaphragm valve 200 may be oriented in many different ways. For example,in an alternative valve body including a weir, the valve passage may beoriented at an angle to promote drainage across the weir when the valveis in the open position, as is common in prior art diaphragm valves.Thus, the designations of top, bottom, upper, lower, side, front, back,and other similar designations are used as a matter of convenience todescribe the preferred embodiment, oriented as it is shown in thedrawing figures, and should not be construed as limiting the scope ofthe invention.

Diaphragm 220 is preferably formed of a flexible plastic or elastomericmaterial. In some ALD systems, diaphragm 220 is preferably formed of athin, molded disc of a plastic material such as polytetrafluoroethylene(“PTFE”), which may be of the type sold by E. I. du Pont de Nemours &Company, Wilmington, Del., USA, under the TEFLON® trademark. PTFE is apreferred diaphragm material for use in a precursor delivery system thatdelivers aluminum chloride (AlCl₃) to the reaction chamber 112. WhilePTFE is desirable for its purity, inertness, chemical resistance, heatresistance, and toughness, other plastic materials, such aspolyvinylidene fluoride (“PVDF”), for example, may also be suitable foruse in diaphragm 220. In ALD systems used in semiconductormanufacturing, diaphragm 220 may preferably be formed of an elastomermaterial, such as VITON® brand fluoroelastomer (FKM) made by DuPont DowElastomers LLC, Wilmington, Del., USA. Other suitable elastomericmaterials for diaphragm 220 include ethylene propylene diene monomer(“EPDM”); silicone rubber; nitrile rubber; chloroprene rubber(neoprene); natural rubber; and perfluorinated elastomers (FFKM), suchas KALREZ® made by DuPont Dow Elastomers LLC, CHEMRAZ® made by Greene,Tweede & Co., Medical & Biotechnology Group, Hatfield, Penn., USA, andSIMRIZ® sold by Freudenberg-NOK, Plymouth, Mich., USA. In some ways,elastomers are less desirable than plastics due to the inferiorhigh-temperature resistance of elastomers and the tendency of fillers insome elastomers to contaminate precursor materials flowing through valvepassage 214. However, elastomers such as VITON, EPDM, and others havegood chemical resistance, good purity, and excellent sealingcapabilities, making them preferred diaphragm materials for use withmany of the ALD precursors used in semiconductor processing.Alternatively, diaphragm 220 may be formed of metal, especially when thetemperature of the medium will exceed 260° C., having the potential todegrade elastomer materials. However, metal diaphragms are morevulnerable to fatigue-related failure and breakage than plastic andelastomeric diaphrams. Diaphram 220 is preferably formed of a solid discof material, but may also include structures that are not disc shaped,composite structures, and any other flexible shapes and structures thatcan be transitioned between open and closed positions. Thus, the term“diaphragm” is to be construed broadly to include any member that bothborders valve passage 214 when open and can be moved or flexed to aclosed position, thereby blocking valve passage 214.

To help prevent corrosion and/or buildup of precursor materials in flowpath 110, the valve passage 214, diaphragm 220, and valve seat 230 maybe coated with a passivation layer. The passivation layer may comprisean oxide, such as Al₂O₃, ZrO₂, HfO₂, TiO₂, Ta₂O₅, SnO₂, or Nb₂O₅; anitride, such as AlN, ZrN, HfN, TiN, TaN, NbN, or BN; a carbide, such asTiC, TaC, ZrC, or HfC; or mixtures thereof. However, other passivationmaterials and coatings may be used. Passivation is particularlyimportant when using halide-based precursors, to prevent exchangereactions between the halide-based precursors and the metal typicallyused in valve body 210 and valve seat 230. The specific composition ofthe passivation layer is selected for compatibility with the type ofprecursor or other medium with which diaphragm valve 200 is used. Otherconsiderations, such as thermal properties, electrical properties,durability, and malleability, for example, may also be important factorsin the selection of the material used for passivation.

Actuator 240 is operably coupled to diaphragm 220 for applying anactuation force for transitioning diaphragm 220 from the open positionto the closed position. In an alternative embodiment, actuator 240transitions diaphragm 220 from the closed position to the open position,or in both directions. However, the preferred diaphragm valve 200 foruse in precursor material delivery system 100 is of a normally closedconfiguration. Actuator 240 preferably includes a solenoid 246 that canbe energized by application of an electric current to drive a plunger250 that transmits force to diaphragm 220. Solenoid 246 is the preferredactuator for diaphragm valve 200 due to its speed and generally lowmaintenance requirements. Alternatively, actuator 240 may include adifferent means for actuating diaphragm 220, such as a pneumatic orhydraulic cylinder, for example. Other devices and methods of actuatingdiaphragm 220, such as piezoelectric devices, for example, may also beused.

Plunger 250 of actuator 240 includes a first end section 256 engaged bysolenoid 246 and a second end section 258 coupled to diaphragm 220.Plunger 250 may be coupled to diaphragm 220 in many ways. For example,diaphragm 220 may include a head 262 or ball end that extends fromsecond side 236 of diaphragm 220 and snaps into lateral openings 266(FIG. 3) in second end section 258 of plunger 250. This snap-fitconnection between head 262 and plunger 250 allows actuator 240 to pullthe central section of diaphragm 220 away from valve seat 230. It mayalso allow diaphragm 220 to be conveniently removed for repair orreplacement without completely disassembling actuator 240, plunger 250,and other components of diaphragm valve 200.

Actuator 240 includes a stop 276 secured to solenoid 246 at its distalend 278 and extending into the center of solenoid 246 to limit outwardtravel of plunger 250. Stop 276 is preferably formed of a magneticmaterial (i.e., a material having a high permeance) to reduce thereluctance in the magnetic circuit of solenoid 246. More specifically,stop 276 reduces the high-reluctance air gap between distal end 278 ofsolenoid 246 and plunger 250, thereby reducing the overall reluctance inthe magnetic circuit and intensifying the magnetomotive force exerted onplunger 250 by solenoid 246, when energized. The magnetomotive actuationforce is further increased as plunger 250 moves closer to stop 276,i.e., when the low permeance gap between plunger 250 and stop 275 isreduced. In other embodiments, stop 276 is made of a nonmagneticmaterial or omitted entirely. A spring 280, preferably interposedbetween stop 276 and plunger 250, biases plunger 250 and diaphragm 220toward the closed position wherein first side 234 of diaphragm 220 ispressed against valve seat 230 to block valve passage 214. Spring 280 ispreferably seated in a counterbore in first end section 256 of plunger250, but alternative embodiments may involve placement of spring 280 inanother location or use of other means for biasing plunger 250 relativeto valve seat 230. For example, in a normally open embodiment (notshown) plunger 250 is biased away from valve seat 230, and plunger 250is driven toward valve seat 230 when actuator 240 is activated. In yetother embodiments, spring 280 may be omitted, in which case diaphragm220 may be driven in both the opening and closing directions by actuator240. In yet another embodiment, spring 280 is omitted and diaphragm 220has a domed shape that is inherently resilient, providing an integralreturn spring force. Skilled persons will appreciate that many othermeans and devices may be employed for effecting return of diaphragm 220to its normal position.

Preferably, diaphragm 220 is secured to valve body 210 by a heating body290 to form a substantially hermetic seal along a perimeter of diaphragm220 where it is clamped against rim 228 by heating body 290. Heatingbody 290 includes a proximal end 294 that is relieved to define a space296 adjacent second side 236 of diaphragm 220. Space 296 providesclearance for diaphragm 220 when diaphragm 220 is moved to the openposition (FIG. 4) and is substantially enclosed, although a small amountof clearance is provided around plunger 250 to allow plunger 250 to movefreely in response to activation of actuator 240. For valves used in ALDsystems, the clearance around plunger 250, the space 296, and any otherpassages in fluid communication with space 296 are preferably sealed toprevent leakage beyond valve 200 in the event that precursor or othermedium escapes around the perimeter of diaphragm 220 or in the eventthat diaphragm 220 ruptures. However, it may not be necessary tohermetically seal space 296, particularly when diaphragm valve 200 isused in applications other than ALD systems. In the preferredembodiment, enclosed space 296 is defined, at least in part, by proximalend 294 of heating body 290. However, in alternative embodiments (notshown), space 296 is defined by one or more other components ofdiaphragm valve 200, such as, for example, the valve body, the actuatorhousing, a valve stem, or another structural member extending proximalto second side 236 of diaphragm 220.

To relieve pressure behind diaphragm 220, space 296 is preferablyvented. Venting of enclosed space 296 may provide one or more benefits.For example, venting can reduce or prevent resistance to the movement ofdiaphragm 220 that would otherwise be caused by compression or expansionof gases trapped in space 296. When the medium flowing through valvepassage 214 has a lowered operating pressure, as is the case in an ALDprecursor material supply, suction may be applied in conjunction withventing to reduce a pressure differential acting on diaphragm 220.Suction can also be applied to generate a vacuum of the same pressure asthe medium in valve passage 214, thereby equalizing the pressures onrespective first and second sides 234 and 236 of diaphragm 220. In someembodiments, suction can be applied to venting to achieve a pressure inspace 296 that is slightly less than the medium in valve passage 214, tothereby assist actuator 240 in opening diaphragm 220. Thus, in thepreferred embodiment, the venting may advantageously reduce the forcenecessary to actuate diaphragm 220 and move it to the open position, andmay also reduce the spring force necessary to return diaphragm 220 tothe closed position. Similar force reductions are possible in analternative normally open configuration, in which case the direction ofactuation and spring forces would be reversed. By reducing forces neededto transition diaphragm 220 between the open and closed positions,venting may also extend the life of diaphragm 220 and prevent solenoidburnout. Extending the life of valves 104 a–e in ALD precursor materialdelivery system 100 can significantly decrease downtime and improveyields in ALD reactor 102. Applying suction to space 296 has the furtherbenefit of improving safety, in that any gas that leaks around orthrough diaphragm 220 is pumped away. This feature is of particularbenefit when using toxic precursor materials, which might otherwise leakinto human workspaces. Applying a vacuum to space 296 also reduces thedensity of gas in valve space 296, which restricts a convective pathwayfrom diaphragm 220 to actuator 240.

Venting is preferably accomplished by a venting passage, an embodimentof which is described below with reference to FIGS. 2 and 3. FIG. 3 is across section view of diaphragm valve 200 taken along lines 3—3 of FIG.2. With reference to FIGS. 2 and 3, the venting passage includes a firstvent passage section 302 extending through heating body 290 andcommunicating with space 296; a second vent passage section 306 passingthrough valve body 210; and an annular connecting passage 310 thatextends around a mid-section of heating body 290 to link together thefirst and second vent passage sections 302 and 306. In other embodiments(not shown), the venting passage follows a different path, through oneor more other parts of diaphragm valve 200. The formation of at least aportion of the venting passage in valve body 210 and, particularly, inbody 122 of module 120, provides a convenient means for connecting apump 316 or other source of suction to second vent passage section 306.More specifically, connection of pump 316 to the venting passage mayinclude connecting the pump 316 to a manifold (not shown) that servesone or more of the diaphragm valves 104 a–104 e and, possibly, othermodules 120 of precursor material delivery system 100 where suction isneeded. Pump 316 is operable to draw a vacuum in space 296 relative tothe pressure outside of valve body 210 (typically atmospheric pressure).

Resilient seals 328 and 382 are provided to prevent leakage aroundheating body 290 and to allow a vacuum to be achieved in space 296behind diaphragm 220. As used herein, the term “vacuum” is used looselyto describe a fluid pressure that is lowered from its atmospheric orotherwise normal pressure. The suction generated by pump 316 preferablyreduces the pressure in space 296 to a pressure that is the same as orclose to the fluid pressure of the medium flowing through valve passage214, thereby equalizing or nearly equalizing a differential force ondiaphragm 220. In an alternative embodiment for use with a high-pressuremedium, the pressure in space 296 is increased by application of apositive fluid pressure instead of suction. However, changing the fluidpressure in space 296 is optional and, therefore, pump 316 may beomitted in some embodiments. In a preferred ALD precursor materialdelivery system 100, pump 316 or another means for generating suction isoperable to reduce the pressure in space 296 to between approximately0.1 mbar and approximately 20 mbar, which is comparable to the operatingpressure of precursor vapors in flow path 110 and valve passage 214.

Diaphragm valve 200 preferably includes features that enhancereliability when valve 200 is used to control the flow of a hightemperature medium, such as an ALD precursor vapor used for depositing athin film on a semiconductor wafer substrate, for example. The improvedthermal design of diaphragm valve 200 may provide advantages overconventional diaphragm valves, in which solenoid actuators (or othertypes of actuators) are vulnerable to heat-related failure. For example,one conventional solenoid-actuated diaphragm valve is rated foroperating temperatures of up to 140° C. When the operating temperatureexceeds 140° C., the solenoid can overheat and melt a plastic bobbinsupporting the solenoid coil and/or melt insulation around the coilwindings, thereby causing blockage of the plunger, short circuiting ofthe coil, and other modes of failure. In non-solenoid valves, highoperating temperatures can cause failure due to permanent deformation ofstructural components, melting or deformation of resilient sealmaterials in the actuator, and other causes.

Heat conducted to actuator 240 can also cool diaphragm 220 or valve body210 enough to cause the medium to condense or freeze within valvepassage 214 or on surfaces bordering valve passage 214. Condensation ofthe medium is particularly troublesome in an ALD precursor materialdelivery system 100, because particles or condensation can causeblockage in the delivery system 100 or may propagate into the reactionchamber 112, causing flaws in the films being formed. Condensation onthe surfaces of diaphragm 220 and/or valve seat 230 can also causeleakage of precursor past valve 200, when closed, which can causenon-ALD growth in reaction chamber 112.

The operating temperature will depend on the vapor pressure of theparticular precursor medium, but will typically be in the range of 130°C. to 220° C. To prevent condensation or freezing of the precursor gasesas they travel along flow path 110, the precursor is gradually heatedwith a positive temperature gradient toward reaction chamber 112. In thepreferred embodiment, the heat is provided by heaters 116 and 118 in twozones along precursor material delivery system 100, although a differentnumber of zones and heaters may be used in an alternative embodiment(not shown). Heat may be provided by means other than electric heaters,but will generally result in the conduction of heat into valve body 210.To evenly and smoothly distribute heat along flow path 110, valve body210 and bodies 122 of other modules 120 are preferably formed of athermally conductive material such as aluminum, titanium, or stainlesssteel.

Heating body 290 is positioned in thermal contact with valve body 210and extends proximal to second side 236 of diaphragm 220 to thereby forma thermally conductive pathway between valve body 210 and diaphragm 220.The thermally conductive pathway facilitates maintenance of an operatingtemperature at diaphragm 220 sufficient to prevent condensation in valvepassage 214. Heating body 290 is interposed between diaphragm 220 andactuator 240 and includes a central opening 322 in alignment withdiaphragm 220 and actuator 240, and through which plunger 250 extendsfor coupling actuator 240 to diaphragm 220. Second end section 258 ofplunger 250 is preferably formed of a thermally conductive material andsized to closely but slidably fit within central opening 322, so thatheat is readily transmitted from heating body 290 to diaphragm 220through plunger 250. A core 326 of heating body 290 extends into acounterbore in valve body 210 above rim 228 and is shaped to define theannular connecting passage 310 (FIG. 3). A seal 328, such as an O-ring,is positioned around core 326 to form a hermetic seal between heatingbody 290 and valve body 210 at an axially distal location relative toannular connecting passage 310. A flange 332 of heating body 290 extendsradially outward from core 326 adjacent an outer surface 334 of valvebody 210. Flange 332 contacts outer surface 334 along a relatively largearea, thereby improving heat conduction from valve body 210 to heatingbody 290. Flange 332 also provides a structure suitable for securingheating body 290 to valve body 210, for example, with one or more screwsor other fasteners 392 (FIGS. 2–3). Flange 332 also compresses seal 328against valve body 210 when secured by fasteners 392. Heating body 290is preferably comprised of a material having a high thermalconductivity, such as aluminum, stainless steel, titanium, copper, orother metals, for example.

When diaphragm 220 is in the closed position in contact with valve seat230, heat is conducted to diaphragm 220 via valve seat 230. Conductionfrom valve seat 230 helps replace in diaphragm 220 the heat lost bydissipation through plunger 250 and actuator 240 into the surroundingenvironment. Valve seat 230 is, accordingly, formed of a material havinga relatively high thermal conductivity, such as aluminum, titanium, oranother metal, for example. When used with a diaphragm made of anelastomeric material, valve seat 230 preferably includes a substantiallyflat annular seating surface 342 extending radially from inlet 216.Seating surface 342 provides increased contact area between diaphragm220 and valve seat 230 when diaphragm 220 is closed. The increasedcontact area reduces the contact resistance (thermal) between valve seat230 and diaphragm 220. Preferably valve seat 230 contacts a substantialportion of first side 234 of diaphragm 220 to promote heat transfer fromvalve seat 230 to diaphragm 220 along a thermally effective contact areaopposite where plunger 250 contacts second side 236 of diaphragm. In thepreferred embodiment, the area of contact between seating surface 342and diaphragm 220 is comparable to the contact area between plunger 250and diaphragm 220. When diaphragm 220 is closed, valve seat 230 maycontact between approximately 5% and 100% of the portion of first side234 of diaphragm 220 exposed to central chamber 232. More preferably,valve seat 230 may contact between approximately 12% and 50% of theexposed area of first side 234 of diaphragm 220, when diaphragm 220 isclosed.

Seating surface 342 may also be polished or otherwise made smooth tofurther reduce contact resistance and to reduce leakage of mediumbetween valve seat 230 and diaphragm 220 when diaphragm 220 is in theclosed position. A passivation layer over first side 234 of diaphragm220 can further enhance conduction of heat from valve seat 230 todiaphragm 220. For example, a passivation layer on first side 234 maycomprise a layer of aluminum oxide (Al₂O₃) or another metallic coatinghaving a thickness of between approximately 10 nm and approximately 100nm.

FIG. 5 is a cross sectional view of an alternative embodiment diaphragmvalve 500 including a plastic diaphragm 520. With reference to FIG. 5,plastic diaphragm 520 is preferably formed of PTFE or another resilient,high-purity, chemically inert material, such as PVDF, for example.Because plastic diaphragm 520 does not seal as easily as elastomericdiaphragms, diaphragm valve 500 includes a modified valve seat 530having a ring-shaped seating ridge 522 that extends upwardly fromseating surface 542 toward diaphragm 520. Seating ridge 522 issufficiently prominent and sized to permanently deform first side 534 ofdiaphragm 520 when diaphragm 520 is pressed against valve seat 530.Seating ridge 522 surrounds inlet 516 and is preferably locatedimmediately adjacent inlet 516 to reduce the amount of spring forcenecessary to cause permanent deformation of diaphragm 520. However, inother embodiments (not shown) seating ridge 522 may be located outwardlyof inlet 516 or in another location. Seating ridge 522 may beflat-topped, as shown in FIG. 5, or may have another shape, such as aknife edge. However, seating ridge 522 differs from knife-edge valveseats of the prior art in that seating ridge 522 is short enough toallow the first side 534 of diaphragm 520 to be pressed against thesurrounding seating surface 542 after seating ridge 522 has formed aring-shaped hit channel 544 in first side 534. In comparison, becauseparticles in some environments can lodge on flat surfaces and interferewith closure of the diaphragm, prior art diaphragm valves prevent leaksby using sharp valve seats that are tall enough to prevent areal contactbetween the diaphragm and flat surfaces around the sharp seating edge.In the context of an ALD precursor material delivery system, sealinginterference is best prevented by improved heat transfer between thevalve seat 530 and diaphragm 520, to prevent particle formation due tocooling of the diaphragm.

Seating ridge 522 is preferably between approximately 0.5 mm and 1.5 mmin height above seating surface 542 to provide the desired permanentdeformation of hit channel 544, while allowing areal contact betweenfirst side 534 of diaphragm 520 and seating surface 542 of valve seat530 after hit channel 544 has been formed. The initial formation of hitchannel 544 in first side 534 of diaphragm 520 may require a break-inperiod in which valve 500 is cycled prior to use. To provide theincreased contact area between valve seat 530 and diaphragm 520 thatpromotes heat transfer, annular seating surface 542 may be sized andshaped similarly to that of the seating surface 342 of the embodiment ofFIGS. 2–4, described above. For example, the area of contact betweenseating surface 542 and diaphragm 520 may be comparable to the contactarea between a second end section 558 of plunger 550 and a second side536 of diaphragm 520. When diaphragm 520 is closed, valve seat 530 maycontact between approximately 5% and 100% of the portion of first side534 of diaphragm 520 exposed to central chamber 532 and, morepreferably, between approximately 12% and 50% of the exposed area.

Valve seat 530 may include a polished surface finish and/or passivationsimilar to the surface treatments described above in connection withvalve seat 230 (FIGS. 2–4) of the type used with elastomeric diaphragm220. Because the plastic material used in diaphragm 520 of FIG. 5 isstiffer than elastomeric materials of the diaphragm 220 of FIGS. 2–4,flexibility may be improved in diaphragm 520 by reducing the thicknessof diaphragm 520 or, preferably, by forming an annular thin region 552between a head 562 of diaphragm 520 and where diaphragm is mountedagainst a rim 528 of valve body 510. Diaphragm 520 and valve seat 530are preferably rotationally secured to prevent relative rotation thatcan cause leakage due to misalignment between seating ridge 522 and hitchannel 544. Preventing relative rotation between diaphragm 520 andvalve seat 530 also facilitates the formation on first side 534 of amicro-roughness that mates against corresponding micro-roughness ofseating surface 542, to thereby promote a hermetic seal.

Referring again to FIG. 2, a thermally resistive member is preferablyinterposed between valve passage 214 and actuator 240 to restrict orthrottle the transfer of heat from valve passage 214 (i.e., from heatingbody 210 and/or diaphragm 220) to actuator 240. The thermally resistivemember may comprise one or more structures for attenuating heat transferbetween valve passage 214 and actuator 240, or between valve body 210and actuator 240, or between heating body 290 and actuator 240, orbetween actuator 240 and one or more other parts of diaphragm valve 200.

One kind of thermally resistive member comprises a section of reducedcross sectional area between valve passage 214 and/or valve body 210 andactuator 240. For example, plunger 250 may include a hollow region 348between respective first and second end sections 256 and 258. Hollowregion 348 and the surrounding thin cylindrical wall of plunger 250attenuate heat transfer between diaphragm 220 and actuator 240. Asdescribed above, attenuation of heat transfer prevents heat-relatedfailure of solenoid 246 and cooling of diaphragm 220, which canotherwise result in condensation of the medium in valve passage 214.

To further inhibit heat transfer through plunger 250, plunger 250 mayhave a composite construction, wherein first end section 256 is formedof a magnetic material, second end section 258 is formed of a thermallyconductive material (for conducting heat from heating body 290 todiaphragm 220), and an insulating central section 352 between respectivefirst and second end sections 256 and 258. Central section 352 may beformed of a material having a substantially lower thermal conductivitythan second end section 258 or may have a structure resulting in lowerthermal conductivity than second end section 258.

Another kind of thermally resistive member includes a valve stem 360supporting actuator 240 over and apart from heating body 290 and valvebody 210. Valve stem 360 may include a section of reduced crosssectional area 364 for attenuating heat transfer between heating body290 and actuator 240. To increase contact resistance, valve stem 360preferably contacts heating body 290 and/or valve body 210 along only avery small area, if at all. For example, valve stem 360 may be supportedon a small step 368 of a central boss 372 of heating body 290. Aninsulating pedestal 376 formed of a thermally resistive material such asplastic or ceramic may extend around or be positioned around a perimeterof flange 332 of heating body 290 to separate valve stem 360 fromheating body 290. Insulating pedestal 376 may comprise a ring ofinsulating material, or may, alternatively, comprise a set of postsextending from flange 332 about its perimeter.

An elastomeric or plastic seal 382 is positioned around boss 372 andbetween heating body 290 and valve stem 360. Seal 382 prevents leakageof gases between heating body 290 and valve stem 360. An annular deadair space 386 may be formed between valve stem 360 and heating body 290and between seal 382 and insulating pedestal 376. Dead air space 386further insulates valve stem 360 from heating body 290. Actuator 240 maybe secured to valve stem 360 by press fitting of solenoid 246 onto valvestem 360, by adhesives, or by other means. Valve stem 360 and heatingbody 290 are attached to valve body 210 by one or more screws 392extending through holes in the radial portion of valve stem 360 and theflange 332 of heating body 290. Screws 392 are threaded into valve body210 and thermally insulated from valve stem 360 by insulating washers396 positioned under the heads of screws 392. Insulating washers 396 maybe made of a plastic material such as PTFE, for example.

A thermally insulating slide bushing 402 is interposed between plunger250 and actuator 240. Slide bushing 402 is preferably formed of athermally insulating plastic material such as PTFE that also has a lowcoefficient of sliding friction against the inner surface of valve stem360 within which first end section 256 of plunger 250 rides. Slidebushing 402 advantageously may inhibit heat transfer between plunger 250and actuator 240, reduce frictional resistance to movement of plunger250, and reduce wear and particle generation that can foul the movementof plunger 250 within actuator 240.

A blocking member 410 is interposed between plunger 250 and stop 276.Blocking member 410 is preferably comprised of a durable plasticmaterial that cushions the impact of plunger 250 against stop 276 whensolenoid 246 is energized. Cushioning of the impact can prevent crackingof stop 276 and/or plunger 250, thereby preventing the formation ofparticles that can foul the movement of plunger 250 within actuator 240.A suitable plastic material for blocking member 410 is PTFE. Blockingmember 410 may also have thermal insulating properties to attenuate heattransfer between plunger 250 and stop 276 when plunger 250 is in thefully open position, in contact with blocking member 410.

When formed of a nonmagnetic material, such as PTFE or another plastic,blocking member 410 introduces a magnetic discontinuity between stop 276and plunger 250 that can reduce a “release time” after removal ofelectric current from solenoid 246 before spring 280 will begin to moveplunger 250 away from stop 276. The magnetic discontinuity introduced byblocking member 410, in effect, reduces the magnetic field at theextreme distal end of first end section 256 of plunger 250 by providinga nonmagnetic separation between the magnetically conductive stop 276and the magnetically conductive first end section 256 of plunger 250. Byway of further explanation, the attractive magnetic force on plunger 250that is generated by solenoid 246 is not immediately removed whenelectric current to solenoid 246 is cut off. Rather, a certain amount oftime must pass before the magnetic force decays below a threshold atwhich spring 280 can begin to move plunger 250 away from stop 276.Blocking member 410 reduces release time by reducing the holding forcebetween solenoid 246 and plunger 250. Reducing the release time resultsin quicker switching from the on state to the off state, making itpossible to shorten the total open time of diaphragm valve 200.

Prior art diaphragm valves, such as the ones described in U.S. Pat. No.5,326,078 of Kimura and U.S. Pat. No. 6,116,267 of Suzuki et al., forexample, include a valve seat having a sharp seating surface fordeforming the diaphragm or increasing localized pressure on thediaphragm when it is pressed against the valve seat. As described above,diaphragm 220 may be comprised of an elastomeric material such as VITON®or EPDM, for example. When exposed to certain heated precursors andchemicals, such as ZrCI₂, for example, elastomer materials can becomebrittle, making them vulnerable to cracking and shearing against a sharpvalve seat. In the preferred embodiment, seating surface 342 of valveseat 230 is characterized by an absence of sharp features, which mayhelp prevent scoring and eventual shearing or cracking of diaphragm 220.Seating surface 342 is preferably larger than 5 mm² and more preferablylarger than 25 mm². While it is desirable to size valve seat 230 largeenough to prevent diaphragm 220 from shearing, the shape and size ofvalve seat 230 may, nevertheless, be selected so that the biasing forcefrom spring 280 will cause slight surface deformation of first side 234of diaphragm 220. Surface deformation causes first side 234 to betterconform to seating surface 342, thereby reducing leakage of medium thatcan otherwise result from micro-roughness of first side 234 and/orseating surface 342. Surface deformation may include elasticdeformation, or plastic deformation, or both. A smooth or polishedsurface finish of seating surface 342 may further improve the ability ofdiaphragm 220 to provide a leak-tight seal when pressed against seatingsurface 342.

As described above with reference to FIG. 5, when the diaphragm iscomprised of a plastic material such as PTFE or PVDF, a predominantlyflat seating surface may be less desirable. As compared to diaphragmsformed of elastomeric material, a plastic diaphragm 520 (FIG. 5) has agreater hardness and is, thus, more difficult to seal against the valveseat. With reference to FIG. 5, valve seat 530 for use with a plasticdiaphragm 520 preferably includes a seating ridge 522 extending from theseating surface 542 around inlet 516. The seating ridge 522 causesplastic deformation of first side 534 of diaphragm 520 when it ispressed against valve seat 530 during a break-in period. Diaphragm 520can be pre-cycled to help break it in before commencing use of diaphragmvalve 500. Plastic deformation occurring during pre-cycling or abreak-in period imparts a ring-shaped hit channel 544 to diaphragm 520that tightly mates against seating ridge 522 to prevent leakage. Asimilar sharp edge valve seat may also be desirable to increaselocalized sealing pressure when diaphragm 520 is made of metal, althoughit may be unnecessary or undesirable to plastically deform a metaldiaphragm.

To ensure a tight seal, the valve seat 230, 530 and diaphragm 220, 520are secured to the respective valve body 210, 510 and plunger 250, 550to thereby prevent relative rotation. Preventing relative rotationbetween the valve seat and diaphragm ensures that the same location ondiaphragm 220, 520 contacts valve seat 230, 530 in the same place everytime the diaphragm valve 200, 500 is closed.

FIG. 4 is an enlarged cross section view detailing valve passage 214,valve seat 230, and diaphragm 220, with the diaphragm 220 showntransitioned to the open position. With reference to FIG. 4, annularseating surface 342 of valve seat 230 is sufficiently large so thatfirst side 234 of diaphragm 220, when flexed to its slightly convexclosed position, will not contact an outer peripheral edge 418 ofseating surface 342. Seating surface 342 may also be curved along outerperipheral edge 418, as shown in FIG. 4, or may be slightly crowned (notshown), to further prevent scoring or shearing of diaphragm 220. Valveseat 230 is generally pedestal-shaped and includes a threaded neck 422extending opposite seating surface 342. Valve seat 230 is screwed intovalve body 210 to achieve good thermal contact. Preferably, valve seat230 is threaded into an inlet portion of valve passage 214. However, inan alternative embodiment (not shown), inlet 216 and outlet 218 arereversed so that valve seat 230 is threaded into an outlet passageformed in valve body 210. Valve seat 230 may be coated with apassivation layer in a manner similar to diaphragm 220 and valve passage214 (as described above) to prevent corrosion of valve seat 230 orbuildup of precursor materials on seating surface 342 or inside inlet216. A seat O-ring 430 is interposed between an upper pedestal portionof valve seat 230 and a lower surface of blind bore 226 of valve body210 to provide a leak-tight seal between valve seat 230 and valve body210. A spacer ring 440 or shim is interposed between upper pedestalportion of valve seat 230 and a floor of blind bore 226 of valve body210 for establishing an axial position of valve seat 230 relative tovalve body 210. Spacer ring 440 prevents overcompression of O-ring 430and establishes an axial position of seating surface 342 relative tovalve body 210 and diaphragm 220. Precise axial positioning of seatingsurface 342 allows for improved control of the seating pressure ofdiaphragm 220 against seating surface 342, thereby enhancingleak-tightness without applying excessive force that might cause scoringon first side 234 of diaphragm 220.

It will be obvious to those having skill in the art that many changesmay be made to the details of the above-described embodiments of thisinvention without departing from the underlying principles thereof. Thescope of the present invention should, therefore, be determined only bythe following claims.

1. A diaphragm valve for a thin film deposition system, comprising: avalve body defining a valve passage having an inlet and an outlet; avalve seat adjacent the valve passage; a flexible diaphragm having firstand second sides, the diaphragm positioned adjacent the valve passageopposite the valve seat with the first side facing toward the valveseat, the diaphragm operable in response to an applied actuation forceto flex between an open position whereby the valve passage is at leastpartially open and a closed position whereby a portion of the first sideof the diaphragm is pressed against the valve seat to thereby block thevalve passage and facilitate heat transfer between the valve seat andthe diaphragm; and a heating body thermally contacting the valve bodyand extending proximal to the second side of the diaphragm, therebyforming a thermally conductive pathway from the valve body to proximalof the second side of the diaphragm that facilitates maintaining anoperating temperature at the diaphragm.
 2. In combination with adiaphragm valve according to claim 1, a heater in thermal associationwith the valve body, the heater adapted to generate heat that isconducted through the valve body and the heating body to thereby preventa medium in the valve passage from condensing or freezing in the valvepassage.
 3. A diaphragm valve according to claim 1 further comprising:an actuator for driving the diaphragm; and a thermally resistive memberinterposed between the valve passage and the actuator for attenuatingheat transfer between the valve passage and the actuator.
 4. A diaphragmvalve according to claim 1 wherein the diaphragm is comprised of aplastic material.
 5. A diaphragm valve for a thin film depositionsystem, comprising: a valve body defining a valve passage having aninlet and an outlet; a valve seat adjacent the valve passage; a flexiblediaphragm having first and second sides, the diaphragm positionedadjacent the valve passage opposite the valve seat with the first sidefacing toward the valve seat, the diaphragm operable in response to anapplied actuation force to flex between an open position whereby thevalve passage is at least partially open and a closed position whereby aportion of the first side of the diaphragm is pressed against the valveseat to thereby block the valve passage and facilitate heat transferbetween the valve seat and the diaphragm; a solenoid for actuating thediaphragm; and means for attenuating heat transfer between the valvepassage and the solenoid.
 6. A diaphragm valve according to claim 5wherein the diaphragm is comprised of a plastic material.
 7. A precursormaterial delivery system including a diaphragm valve comprising: a valvebody defining a valve passage having an inlet and an outlet; a valveseat adjacent the valve passage; and a flexible diaphragm having firstand second sides, the diaphragm positioned adjacent the valve passageopposite the valve seat with the first side facing toward the valveseat, the diaphragm operable in response to an applied actuation forceto flex between an open position whereby the valve passage is at leastpartially open and a closed position whereby a portion of the first sideof the diaphragm is pressed against the valve seat to thereby block thevalve passage and facilitate heat transfer between the valve seat andthe diaphragm; and a solenoid for actuating the diaphragm.
 8. Aprecursor material delivery system according to claim 7, furthercomprising a heater in thermal association with the valve body.
 9. Aprecursor material delivery system according to claim 7 wherein aseating surface of the diaphragm valve contacts between approximately 5%and 100% of the first side of the diaphragm when closed.
 10. A precursormaterial delivery system according to claim 7 wherein a seating surfaceof the diaphragm valve contacts between approximately 12% and 50% of thefirst side of the diaphragm when closed.
 11. A precursor materialdelivery system according to claim 7 wherein a seating surface of thediaphragm valve is characterized by an absence of sharp features,thereby preventing shearing of the diaphragm.
 12. A precursor materialdelivery system according to claim 7 wherein the valve seat is polished,thereby improving heat transfer from the valve seat to the diaphragmwhen the first side of the diaphragm is pressed against the valve seat.13. A precursor material delivery system according to claim 7 whereinthe diaphragm of the diaphragm valve is comprised of a plastic material.14. A precursor material delivery system according to claim 7 furthercomprising a spacer ring interposed between the valve seat and the valvebody to establish an axial position of the valve seat relative to thevalve body.
 15. A precursor material delivery system according to claim7 further comprising a protective coating over the first side of thediaphragm.
 16. A precursor material delivery system according to claim15 wherein the protective coating is selected from the group consistingof an oxide, a nitride, a carbide, and mixtures thereof.
 17. A precursormaterial delivery system according to claim 7 further comprising aprotective coating lining the valve passage.
 18. A precursor materialdelivery system according to claim 17 wherein the protective coating isselected from the group consisting of an oxide, a nitride, a carbide,and mixtures thereof.
 19. A precursor material delivery system accordingto claim 7 further comprising a protective coating over a seatingsurface of the valve seat against which the diaphragm presses when inthe closed position.
 20. A precursor material delivery system accordingto claim 19 wherein the protective coating is selected from the groupconsisting of an oxide, a nitride, a carbide, and mixtures thereof. 21.An ALD reactor including a diaphragm valve comprising: a valve bodydefining a valve passage having an inlet and an outlet; a valve seatadjacent the valve passage; and a flexible diaphragm having first andsecond sides, the diaphragm positioned adjacent the valve passageopposite the valve seat with the first side facing toward the valveseat, the diaphragm operable in response to an applied actuation forceto flex between an open position whereby the valve passage is at leastpartially open and a closed position whereby a portion of the first sideof the diaphragm is pressed against the valve seat to thereby block thevalve passage and facilitate heat transfer between the valve seat andthe diaphragm; and a solenoid for actuating the diaphragm.
 22. An ALDreactor according to claim 21, further comprising: an enclosed spaceadjacent the second side of the diaphragm; a venting passage incommunication with the enclosed space; and a pump operably coupled tothe venting passage for reducing a fluid pressure in the enclosed space.23. An ALD reactor according to claim 22 wherein the venting passageextends through the valve body.
 24. An ALD reactor according to claim 21wherein a seating surface of the valve seat contacts betweenapproximately 5% and 100% of the first side of the diaphragm whenclosed.
 25. An ALD reactor according to claim 21 wherein a seatingsurface of the valve seat contacts between approximately 12% and 50% ofthe first side of the diaphragm when closed.
 26. An ALD reactoraccording to claim 21 wherein the valve seat is characterized by anabsence of sharp features, thereby preventing shearing of the diaphragm.27. An ALD reactor according to claim 21 wherein the diaphragm of thediaphragm valve is comprised of a plastic material.
 28. A precursormaterial delivery system including a diaphragm valve comprising: a valvebody defining a valve passage having an inlet and an outlet; a valveseat adjacent the valve passage; and a flexible diaphragm having firstand second sides, the diaphragm positioned adjacent the valve passageopposite the valve seat with the first side facing toward the valveseat, the diaphragm operable in response to an applied actuation forceto flex between an open position whereby the valve passage is at leastpartially open and a closed position whereby a portion of the first sideof the diaphragm is pressed against the valve seat to thereby block thevalve passage and facilitate heat transfer between the valve seat andthe diaphragm, wherein the valve seat is polished, thereby improvingheat transfer from the valve seat to the diaphragm when the first sideof the diaphragm is pressed against the valve seat.
 29. A precursormaterial delivery system including a diaphragm valve comprising: a valvebody defining a valve passage having an inlet and an outlet; a valveseat adjacent the valve passage; and a flexible diaphragm having firstand second sides, the diaphragm positioned adjacent the valve passageopposite the valve seat with the first side facing toward the valveseat, the diaphragm including a protective coating over the first sidethereof, and the diaphragm operable in response to an applied actuationforce to flex between an open position whereby the valve passage is atleast partially open and a closed position whereby a portion of thefirst side of the diaphragm is pressed against the valve seat to therebyblock the valve passage and facilitate heat transfer between the valveseat and the diaphragm.
 30. A precursor material delivery systemaccording to claim 29 wherein the protective coating is selected fromthe group consisting of an oxide, a nitride, a carbide, and mixturesthereof.
 31. A precursor material delivery system according to claim 30,in which the diaphragm is comprised of a plastic material.
 32. Aprecursor material delivery system including a diaphragm valvecomprising: a valve body defining a valve passage having an inlet and anoutlet; a valve seat adjacent the valve passage; and a flexiblediaphragm having first and second sides, the diaphragm positionedadjacent the valve passage opposite the valve seat with the first sidefacing toward the valve seat so that an exposed area of the first sideborders the valve passage, the diaphragm operable in response to anapplied actuation force to flex between an open position whereby thevalve passage is at least partially open and a closed position wherebybetween approximately 5% and 100% of the exposed area of the first sideof the diaphragm is pressed against the valve seat to thereby block thevalve passage and facilitate heat transfer between the valve seat andthe diaphragm.
 33. A precursor material delivery system according toclaim 32 wherein between approximately 12% and 50% of the exposed areaof the first side of the diaphragm is pressed against the valve seatwhen the diaphragm is in the closed position.